Self-clinkering NF4 + compositions for NF3 -F2 gas generators and method of producing same

ABSTRACT

Improved NF 4   +  compositions for solid propellant NF 3  -F 2  gas generators are described which produce NF 3  and F 2  free of gaseous Lewis acids and do not require clinker forming additives for their complexing. The novel self-clinkering compositions (NF 4 ) 2  SnF 6 , NF 4  SnF 5 , (NF 4 ) 2  TiF 6 , NF 4  Ti 2  F 9 , NF 4  Ti 3  F 13 , and NF 4  Ti 6  F 25  and processes for their production are disclosed.

The invention herein described was made in the course of or under a contract or subcontract thereunder, (or grant) with the United States Navy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of Ser. No. 734,153 filed Oct. 20, 1976, and now U.S. Pat. No. 4,152,406.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to compositions of matter and methods of producing the same and is particularly directed to improved solid propellant NF₃ --F₂ gas generators derived from self-clinkering NF₄ ⁺ salts, together with methods for producing such gas generators.

2. Description of the Prior Art

NF₄ ⁺ salts are the key ingredients for solid propellant NF₃ --F₂ gas generators, as shown by D. Pilipovich in U.S. Pat. No. 3,963,542. These propellants consist of a highly over-oxidized grain using NF₄ ⁺ salts as the oxidizer. Burning these propellants with a small amount of fuel, such as aluminum powder, generates sufficient heat to thermally dissociate the bulk of the oxidizer. This is shown for NF₄ BF₄ in the following equation:

    NF.sub.4 BF.sub.4 →NF.sub.3 +F.sub.2 +BF.sub.3

as can be seen from the equation the gaseous combustion products contain the volatile Lewis acid BF₃. This disadvantage of a volatile Lewis acid byproduct is shared by all the previously known NF₄ ⁺ compositions. These volatile Lewis acids possess a relatively high molecular weight and a low γ value (γ=C_(pi) /C_(vi)), relative to the preferred diluent helium and frequently act as a deactivator for the chemical HF-DF laser. Consequently, these volatile Lewis acids must be removed from the generated gas prior to its use in an efficient chemical laser. Based on the state of the art, heretofore, this would be achieved by adding a clinker forming agent, such as KF, to the solid propellant formulation. The function of this additive served to convert the volatile Lewis acid, such as BF₃, to a non-volatile salt as shown by the following equation:

    KF+BF.sub.3 →KBF.sub.4

The principal disadvantages of this approach are that, even if an excess of KF is used, complete clinkering cannot always be guaranteed, and that the addition of the KF severely degrades the yield of NF₃ --F₂ obtainable per pound of formulation. This problem could be solved by using NF₄ ⁺ containing compositions derived from non-volatile Lewis acids. However, the synthesis of such compositions has previously been unknown, since highly stable and non-volatile Lewis acids are polymeric and contain coordination-wise saturated central atoms. Consequently, these compounds possess very little or no acidity, which renders the synthesis of such salts very difficult.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

The above described problem of obtaining a Lewis acid free NF₃ --F₂ gas stream from NF₄ ⁺ compositions without clinker forming additives is overcome by the present invention. We have found that NF₄ ⁺ salts, derived from the polymeric non-volatile Lewis acids SnF₄ (subliming at 704° C.) and TiF₄ (1 atm vapor pressure at 284° C.) can be prepared. The lack of acidity of SnF₄ at temperatures, at which NF₄ ⁺ salts can be formed and exist, was demonstrated. It was shown that mixtures of NF₃, F₂, and SnF₄, when heated to temperatures of up to 300° C. at autogenous pressures of about 150 atm, did not show any evidence for NF₄ ⁺ formation.

Since a direct synthesis of an NF₄ ⁺ salt derived from SnF₄ was not possible, we have studied metathetical and displacement reactions. Because SnF₆ ⁻⁻ salts are stable in anhydrous HF, the metathetical and displacement reactions were carried out in this solvent. The following methathetical reaction

    2NF.sub.4 SbF.sub.6 +Cs.sub.2 SnF.sub.6  .sup.HF solution  2CsSbF.sub.6 ↓+(NF.sub.4).sub.2 SnF.sub.6

was carried out. It resulted in the precipitation of the rather insoluble salt CsSbF₆, while the soluble (NF₄)₂ SnF₆ remained in solution. The two products were separated by a simple filtration step. The composition (in mol%) of the crude product was: (NF₄)₂ SnF₆, 83; NF₄ SbF₆, 13; CsSbF₆, 4. The purity of this product can be easily increased by following the procedures outlined for NF₄ BF₄ in our co-pending application Serial No. , filed .

Another NF₄ ⁺ salt derived from SnF₄ was obtained by the following quantitative displacement reaction in anhydrous HF as a solvent.

    NF.sub.4 BF.sub.4 +SnF.sub.4  .sup.HF solution  NF.sub.4 SnF.sub.5 +BF.sub.3

for TiF₄, the direct synthesis of an NF₄ ⁺ salt from NF₃, F₂, and TiF₄ is still possible, since TiF₄ possesses already some vapor pressure at temperatures where NF₄ ⁺ salts can be formed. However, the product thus obtained is very rich in TiF₄, as shown by the following equation: ##STR1## The NF₄ ⁺ content of this salt could not be significantly increased by any changes in the reaction conditions.

Displacement reactions between NF₄ BF₄ and TiF₄, either in HF solution or in the absence of a solvent, produced NF₄ ⁺ salts according to

    NF.sub.4 BF.sub.4 +nTiF.sub.4 →NF.sub.4 TiF.sub.5.(n-1)TiF.sub.4 +BF.sub.3

where, depending on the exact reaction conditions, n equals either 3 or 2.

A further increase in the NF₄ ⁺ content was possible by the following metathetical reaction which yielded (NF₄)₂ TiF₆ :

    2nf.sub.4 sbF.sub.6 +Cs.sub.2 TiF.sub.6  .sup.HF solution  2CsSbF.sub.6 ↓+(NF.sub.4).sub.2 TiF.sub.6

the separation and purification procedure for this product is analogous to that outlined above for (NF₄)₂ SnF₆.

The advantages of the above disclosed concept of using these novel self-clinkering NF₄ ⁺ composition for NF₃ --F₂ gas generators become obvious from a comparison of their theoretical performance data. In Table I, the theoretical yields of usable fluorine, expressed in weight percent, of (NF₄)₂ SnF₆ and (NF₄)₂ TiF₆ are compared to that of KF clinkered NF₄ BF₄, the highest performing presently known system. The novel self-clinkering compositions clearly outperform KF clinkered NF₄ BF₄. Furthermore, the risk of incomplete clinkering which always exists for a clinkered formulation is avoided.

                  TABLE I                                                          ______________________________________                                         A COMPARISON OF THE THEORETICAL PERFORMANCE                                    OF SELF-CLINKERING (NF.sub.4).sub.2 SnF.sub.6 AND                              (NF.sub.4).sub.2 TiF.sub.6 WITH KF-CLINKERED NF.sub.4 BF.sub.4                  System         Performance (Weight % Usable F)                                ______________________________________                                         NF.sub.4 BF.sub.4 . 1.2KF                                                                      38.5                                                           (NF.sub.4).sub.2 SnF.sub.6                                                                     46.0                                                           (NF.sub.4).sub.2 TiF.sub.6                                                                     55.6                                                           ______________________________________                                    

Accordingly, it is an object of the present invention to provide higher performing solid propellant NF₃ --F₂ gas generator compositions.

Another object of the present invention is to provide self-clinkering NF₄ ⁺ compositions capable of generating Lewis acid free NF₃ and F₂.

Another object of the present invention is to provide processes for the production of self-clinkering NF₄ ⁺ compositions.

These and other objects and features of the present invention will be apparent from the following examples. It is understood, however, that these examples are merely illustrative of the invention and should not be considered as limiting the invention in any sense.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE I

Metathetical reactions were carried out in an apparatus consisting of three Teflon FEP U-traps interconnected by Monel unions and closed off at each end by a Monel valve. The union between trap II and trap III contained a Teflon filter and was held in place by a press fit. The passivated apparatus was taken to the dry box and Cs₂ SnF₆ and NF₄ SbF₆ (in a 1:2 mole ratio) were placed into traps I and II, respectively. The apparatus was connected to the vacuum line through flexible corrugated Teflon FEP tubing. Anhydrous HF, in an amount sufficient to just dissolve the starting materials, was added to traps I and II. Trap I was flexed to allow the Cs₂ SnF₆ solution to run into trap II containing the NF₄ SbF₆ solution. Upon contact of the two solutions, copious amounts of a white precipitate (CsSbF₆) formed. The contents of trap II were agitated for several minutes to obtain good mixing. Then the apparatus was inverted to allow the solution to run onto the filter. To generate a pressure differential across the filter, trap III was cooled to -80° C. After completion of the filtration step, trap III was warmed to ambient temperature and the HF solvent was pumped off. The solid residue on top of the filter consisted mainly of CsSbF₆, whereas the solid collected in trap II was mainly the desired (NF₄)₂ SnF₆.

The following example gives a typical product distribution obtainable with the above procedure and apparatus. Starting materials: NF₄ SbF₆ (9.72 mmol), Cs₂ SnF₆ (4.86 mmol); weight of solid on filter=4.24 g; weight of solid in trap III=1.36 g (weight calcd for 4.86 mmol of (NF₄)₂ SnF₆ =2.01 g). Elemental analysis for solid from trap III. Found: NF₃, 31.5; Sn, 25.1; Sb, 5.9; Cs, 1.3. Calculated analysis for a mixture (mol %) of 82.8 (NF₄)₂ SnF₆, 12.9 NF₄ SbF₆, and 4.3 CsSbF₆ : NF₃, 31.72; Sn, 24.60; Sb, 5.24; Cs, 1.43.

(NF₄)₂ SnF₆ is a white, crystalline, hygroscopic solid, stable at room temperature but decomposing at 240° C. Its characteristic x-ray powder pattern is listed in Table II. Its ionic composition, i.e. the presence of discrete NF₄ ⁺ cations and SnF₆ ⁻⁻ anions was established by ¹⁹ F nmr, infrared and Raman spectroscopy.

The ¹⁹ F nmr spectrum, recorded for a BrF₅ solution, showed in addition to the solvent lines a triplet of equal intensity with φ=-220, J_(NF) =229.6 Hz, and a line width at half height of about 5 Hz, which is characteristic of tetrahedral NF₄ ⁺. In addition, a narrow singlet at φ=149 was observed with the appropriate ^(117/119) Sn satellites (average J_(SnF) =1549 Hz), characteristic of octahedral SnF₆ ⁻⁻. The vibrational spectra of (NF₄)₂ SnF₆ and their assignments are summarized in Table III.

EXAMPLE II

A mixture of NF₄ BF₄ and SnF₄ (9.82 mmol each) was placed into a passivated Teflon-FEP ampoule containing a Teflon coated magnetic stirring bar. Anhydrous HF (10 ml liquid) was added at -78° C., and the resulting suspension was stirred at 25° C. for 2 hours. The volatile material was pumped off at 35° C. leaving behind a white stable solid which, on the basis of its weight (3.094 g) and Raman spectrum, consisted of 83 mol percent NF₄ SnF₅ and 17 mol percent unreacted starting materials. The HF treatment was repeated (again for 2 hours) and the non-volatile residue (2.980 g, weight calcd for 9.82 mmol of NF₄ SnF₅ =2.982 g) was shown by infrared, Raman, and ¹⁹ F nmr spectroscopy to be essentially pure NF₄ SnF₅. Anal. Calcd for NF₄ SnF₅ :NF₃, 23.38; Sn, 39.08. Found: NF₃, 23.6; Sn, 38.7.

                  TABLE II                                                         ______________________________________                                         X-RAY POWDER DATE FOR (NF.sub.4).sub.2 SnF.sub.6.sup.a                         d obsd     d calcd      Int         h k l                                      ______________________________________                                         6.27       6.36         w           1 1 1                                      5.67       5.70         vs          0 0 2                                      4.99       5.04         vw          1 0 2                                      3.67       3.69         w           2 1 2                                      3.55       3.59         s           1 0 3                                      3.42       3.42         s           3 1 0                                      2.990      2.990        s           2 1 3                                      2.851      2.851        ms          0 0 4                                      2.492      2.490        m           3 3 1                                      2.347      2.356        w           3 2 3                                      2.230      2.228        s           4 2 2                                      2.120      2.123        mw          5 1 0                                      2.023      2.024        mw          5 0 2                                      1.961      1.963        w           4 0 4                                      1.917      1.914        m           4 4 0                                      1.882      1.881        mw          5 0 3                                      1.834      1.832        w           5 3 1                                      1.813      1.814        mw          4 4 2                                      1.763      1.765        vw          5 3 2                                      1.712      1.712        w           6 2 0                                      1.686      1.686        m           5 4 0,3 0 6                                1.662      1.662        m           3 1 6                                      1.616      1.614        mw          6 3 0                                      1.570      1.570        mw          5 0 5                                      1.500      1.501        mw          6 4 0                                      1.397      1.396        mw          6 4 3                                      1.387      1.386        w           6 5 0                                      1.359      1.359        mw          7 0 6,5 4 5                                1.331                   mw                                                     1.314                   mw                                                     1.263                   w                                                      1.231                   w                                                      1.212                   mw                                                     1.192                   w                                                      1.177                   mw                                                     ______________________________________                                          .sup.a tetragonal, a = 10.828A, c = 11.406A, Cu K.sub.α radiation N      filter                                                                   

                                      TABLE III                                    __________________________________________________________________________     Vibrational Spectra of Solid (NF.sub.4).sub.2 SnF.sub.6                         Obsd Freq (cm.sup.-1)                                                                           Assignments                                                  and Rel Inten    (Point Group)                                                 IR     Raman     NF.sub.4.sup.+ (T.sub.d)                                                                   SnF.sub.6 --(O.sub.h)                             __________________________________________________________________________     1224 mw          2ν.sub.4 (A.sub.1 + E + F.sub.2                            1160 vs                                                                               1158 (1.5)                                                                               ν.sub.3 (F.sub.2)                                          1132 sh,vw                   ν.sub.1 + ν.sub.3 (F.sub.1μ)             1059 vw          ν.sub.2 + ν.sub.4 (F.sub.1 + F.sub.2)                   1026 vw                      ν.sub.2 + ν.sub.3 (F.sub.1u                                              + F.sub.2u)                                               811 (0.1)                                                                               2ν.sub.2 (A.sub.1 + A.sub.2 + E)                            854 vvw                                                                               853 (10) ν.sub.1 (A.sub.1)                                           613 mw                                                                                613 (5.0)                                                               605 mw                                                                                607 (1.5)                                                                               ν .sub.4 (F.sub.2)                                                 579 (8.3)            ν.sub.1 (A.sub.1g)                              550 vs                      ν.sub.3 (F.sub.1u)                                     470 (0+)                                                                             br             ν.sub.2 (E.sub.g)                                     449 (3.1)                                                                      442 (2.9) ν.sub.2 (E)                                                        251 (3.3)            ν.sub.5 (F.sub.2g)                                     84 (0.3) Lattice Vibration                                             __________________________________________________________________________

NF₄ SnF₅ is a white, crystalline, hygroscopy solid, stable at room temperature and decomposing above 200° C. Its characteristic x-ray powder pattern is listed in Table IV.

                  TABLE IV                                                         ______________________________________                                         X-RAY POWDER DATA FOR NF.sub.4 SnF.sub.5                                       d obsd      Int         d obsd        Int                                      ______________________________________                                         7.72        mw          2.571         mw                                       6.32        vs          2.519         vw                                       5.69        w           2.276         w                                        5.29        w           2.146         w                                        4.51        m           2.064         ms                                       4.19        m           1.965         mw                                       3.80        vs          1.929         w                                        3.46        m           1.820         m                                        3.32        m           1.780         mw                                       3.17        mw          1.757         mw                                       2.868       w           1.732         mw                                       2.802       w           1.700         mw                                       2.743       m           1.661         vw                                       2.683       w           1.639         w                                                                1.615         w                                        ______________________________________                                    

Its ionic structure, i.e., presence of NF₄ ⁺ cations, was established by its ¹⁹ F nmr spectrum in BrF₅ solution. In addition to the solvent lines, it showed the triplet (see above) at φ=-220, characteristic of NF₄ ⁺. Two resonances were observed for SnF₅ ⁻ at φ=145.4 and 162.4, respectively, with an area ratio of 1:4. At -20° C. the resonances consisted of broad lines, but at lower temperatures the φ=162.4 signal showed splittings. Based on a more detailed analysis of these data, the SnF₅ ⁻ anion appears to have a diameric or polymeric structure. The vibrational spectrum of NF₄ SnF₅ is listed in Table V and again establishes the presence of discrete NF₄ ⁺ cations.

EXAMPLE III

When a mixture of NF₄ BF₄ and SnF₄ in a mol ratio of 2:1 was treated 8 times, as described in Example II, with liquid HF for a total of 35 days, the resulting non-volatile residue consisted mainly of NF₄ SnF₅, unreacted NF₄ BF₄, and only a small amount of (NF₄)₂ SnF₆.

EXAMPLE IV

The metathetical synthesis of (NF₄)₂ TiF₆ from saturated HF solutions of NF₄ SbF₆ (10.00 mmol) and Cs₂ TiF₆ (5.00 mmol) was carried out in the apparatus described in Example I for the synthesis of (NF₄)₂ SnF₆. After combination of the solutions of the two starting materials at room temperature and formation of a CsSbF₆ precipitate, the mixture was cooled to -78° C. and filtered. The volatile materials were pumped off at 50° C. for 1 hour. The filter cake (3.85 g) was shown by its x-ray powder diffraction pattern and vibrational spectroscopy to be mainly CsSbF₆ containing, due to the hold up of some mother liquor, a small amount of (NF₄)₂ TiF₆. The filtrate residue (1.55 g, weight calcd for 5 mmol of (NF₄)₂ TiF₆ =1.71 g) had the composition (mol%): 88.5 (NF₄)₂ TiF₆ and 11.5 CsSbF₆. Found: NF₃, 36.2; Ti, 12.21; Sb, 4.11; Cs, 4.4. Calcd for a mixture of 88.5 (NF₄)₂ TiF₆ and 11.5 CsSbF₆ : NF₃, 36.43; Ti, 12.29; Sb, 4.06; Cs, 4.43. Based on the observed Raman spectrum, the composition of the filtrate residue was estimated to be 90 (NF₄)₂ TiF₆ and 10 CsSbF₆, in good agreement with the above elemental analysis.

(NF₄)₂ TiF₆ is a white, crystalline, hygroscopic solid, stable at room temperature, but decomposing above 200° C. Its characteristic x-ray powder pattern is listed in Table VI.

                  TABLE V                                                          ______________________________________                                         Vibrational Spectra of Solid NF.sub.4 SnF.sub.5                                Obsd Freq (cm.sup.-1)                                                          and Rel Intens                                                                 NF.sub.4 SnF.sub.5  Assignments (Point Group)                                  IR         Raman        NF.sub.4.sup.+ (T.sub.d)                               ______________________________________                                         1222 mw                       2ν.sub.4 (A.sub.1 + F + F.sub.2)                             1168 (0.4)                                                      1165 vs        1159 (0.8)     ν.sub.3 (F.sub.2)                                            1150 sh                                                         1134 w,sh                                                                      1061 w                        ν.sub.2 + ν.sub.4 (F.sub.1                                               + F.sub.2)                                       1048 w                                                                                         881 (0.2)     2ν.sub.2 (A.sub.1 + A.sub.2 + E)               850 vw         851 (10)      ν.sub.1 (A.sub.1)                              635 vs                                                                                        622 (9.2)                                                       605 mw         606 (3.3)     ν.sub.4 (F.sub.2)                              575 vs                                                                                        574 (0.5)                                                       559 w, sh      558 (2.0)                                                       490 m          490 (0+)                                                        458 m                                                                                         448 (2.5)                                                                                    ν.sub.2 (E)                                                   440 (2.3)                                                                      272 (0.6)                                                                      247 (1.4)                                                                      222 (1.1)                                                                      197 (0.6)                                                                      154 (0+)                                                                       135 (0.2)                                                      ______________________________________                                    

                  TABLE VI                                                         ______________________________________                                         X-RAY POWDER DATE FOR (NF.sub.4).sub.2 TiF.sub.6.sup.a                         d obsd     d calcd      Int         h k l                                      ______________________________________                                         6.23       6.26         vw          1 1 1                                      5.57       5.56         vs          0 0 2                                      4.93       4.93         w           1 0 2                                      3.49       3.50         s           1 0 3                                      3.39       3.39         s           3 1 0                                      2.94       2.93         ms          2 1 3                                      2.782      2.778        m           0 0 4                                      2.465      2.463        w           3 3 1                                      2.315      2.318        mw          3 2 3                                      2.201      2.200        s           4 2 2                                      2.100      2.101        w           5 1 0                                      1.990      1.990        vw          5 2 0,5 0 2                                1.892      1.894        m           4 4 0                                      1.789      1.789        mw          6 0 0,4 4 2                                1.663      1.664        mw          2 2 6                                      1.641      1.644        mw          3 0 6                                      ______________________________________                                          .sup.a tetragonal, a = 10.715A, c = 11.114A, Cu K.sub.α radiation N      filter                                                                   

Its ionic structure, i.e. the presence of discrete NF₄ ⁺ cations and TiF₆ ⁻⁻ anions was established by ¹⁹ F nmr and vibrational spectroscopy. The ¹⁹ F nmr spectrum showed the triplet at φ=-220, characteristic for NF₄ ⁺ as shown above, and the characteristic TiF₆ ⁻⁻ signal at φ=-81.7. The vibrational spectra are listed in Table VII.

                  TABLE VII                                                        ______________________________________                                         VIBRATIONAL SPECTRA OF SOLID (NF.sub.4).sub.2 TiF.sub.6                        Obsd Freq (cm.sup.-1) and                                                        Rel Intens   Assignments (Point Group)                                       IR       Raman     NF.sub.4.sup.+ (T.sub.d)                                                                      TiF.sub.6.sup.-- (O.sub.h)                   ______________________________________                                         1219 mw            2ν.sub.4 (A.sub.1 + E + F.sub.2)                         1160 vs  1158 (1.4)                                                            1132 sh,vw         ν.sub.3 (F.sub.2)                                        1060 vw            ν.sub.2 + ν.sub.4 (F.sub.1 + F.sub.2)                 1021 w                                                                          910 vw                           ν.sub.1 + ν.sub.4 (F.sub.1μ)                  883 (0.1)                                                                               2ν.sub.2 (A.sub.1 + A.sub.2 + E)                          850 sh,vw                                                                               853 (10) ν.sub.1 (A.sub.1)                                         804 w                                                                          611 mw   612 (5)  ν.sub.4 (F.sub.2)                                                  607 sh                                                                         601 (8.0)               ν.sub.1 (A.sub.1g)                         563 vs                           ν.sub.3 (F.sub.1μ)                      452 vw   450 (3.3)                                                                      442 (2.6)                                                                               ν.sub.2 (E)                                                        289 (8.2)               ν.sub.5 (F.sub.2g)                                  107 (0+)                                                                        86 (2)  Lattice Vibrations                                          ______________________________________                                    

EXAMPLE V

TiF₄ (11.3 mmol), NF₃ (200 mmol), and F₂ (200 mmol) were heated in a passivated 90 ml Monel cylinder to various temperatures for different time periods. After each heating cycle, the volatile products were temporarily removed and the progress of the reaction was followed by determining the weight gain of the solid and recording its vibrational spectra. Heating to 200° C. for 3 days resulted in a weight gain of 8 mg and the vibrational spectra showed mainly unreacted TiF₄ in addition to a small amount of NF₄ ⁺ and a polyperfluorotitanate (IV) anion (probably Ti₆ F₂₅ ⁻) having its strongest Raman line at 784 cm⁻¹. During the next two heating cycles (190°-195° C. for 14 days and 180° C. for 35 days) the solid gained 149 and 41 mg, respectively, in weight. The vibrational spectra did not show any evidence of unreacted TiF₄, and the relative intensities of the bands due to NF₄ ⁺ had significantly increased. Furthermore, the 784 cm⁻¹ Raman line had become by far the most intense Raman line. Additional heating to 230° C. for 3 days did not result in significant changes in either the weight or the vibrational spectra of the solid. Based on the observed weight increase and on the lack of spectroscopic evidence for the presence of lower polyperfluorotitanate (IV) anions, the solid product appears to have the approximate composition NF₄ Ti₆ F₂₅ (calcd weight increase, 205 mg; obsd weight increase 198 mg).

EXAMPLE VI

Displacement reactions were carried out either in HF solution at room temperature or by heating the starting materials in the absence of a solvent in a Monel cylinder. For the HF solution reactions, the solid starting materials (6 mmol of NF₄ BF₄ in each experiment) were placed in a passivated Teflon FEP ampoule and 15 ml of liquid anhydrous HF was added. The mixture was stirred with a Teflon coated magnetic stirring bar at room temperature for a given time period. The volatile products were pumped off at 50° C. for 3 hours and the composition of the solid residue was determined by elemental and spectroscopic analyses and from the observed material balances.

The thermal displacement reactions were carried out in a prepassivated 90 ml Monel cylinder which was heated in an electric oven for a specified time period. The volatile products were separated by fractional condensation in a vacuum line, measured by PVT, and identified by infrared spectroscopy. The solid residues were weighed and characterized by elemental and spectroscopic analyses. The results of these experiments are summarized in Table VIII.

                                      TABLE VIII                                   __________________________________________________________________________     RESULTS FROM THE DISPLACEMENT REACTIONS                                        BETWEEN NF.sub.4 BF.sub.4 AND TiF.sub.4                                          Reactants (mol)                                                                             Reaction Conditions                                                                  Products (mol)                                            __________________________________________________________________________     NF.sub.4 BF.sub.4 (6), untreated TiF.sub.4 (6)                                                HF, 24° C., 18h                                                                   NF.sub.4 Ti.sub.2 F.sub.g (4), NF.sub.4 BF.sub.4                               (4)                                                   NF.sub.4 BF.sub.4 (6), untreated TiF.sub.4 (12)                                               HF, 24° C., 72h                                                                   NF.sub.4 Ti.sub.2 F.sub.9 (6)                         NF.sub.4 BF.sub.4 (6), prefluor. TiF.sub.4 (6)                                                HF, 24° C., 138h                                                                  HF.sub.4 Ti.sub.3 F.sub.13 (˜2), NF.sub.4                                BF.sub.4 (˜4),                                                           small amount of NF.sub.4 Ti.sub.2 F.sub.9             NF.sub.4 BF.sub.4 (6), prefluor. TiF.sub.4 (12)                                               HF, 24° C., 96h                                                                   NF.sub.4 Ti.sub.3 F.sub.13 (4), NF.sub.4                                       BF.sub.4 (2),                                         NF.sub.4 BF.sub.4 (6), untreated TiF.sub.4 (6)                                                190° C., 18h                                                                      NF.sub.4 Ti.sub.2 F.sub.9 (˜3), NF.sub.3                                 (˜3), BF.sub.3 (˜6),                                               small amounts of NF.sub.4 BF.sub.4 and NF.sub.4                                Ti.sub.3 F.sub.13                                     NF.sub.4 BF.sub.4 (6), untreated TiF.sub.4 (6)                                                160° C., 60h                                                                      NF.sub.4 Ti.sub.3 F.sub.13 (2), NF.sub.4                                       BF.sub.4 (1.4), NF.sub.3 (2.6),                                                BF.sub.3 (4.6)                                        NF.sub.4 BF.sub.4 (6), prefluor. TiF.sub.4 (6)                                                170° C., 20h                                                                      NF.sub.4 Ti.sub.2 F.sub.9 (3) NF.sub.4 BF.sub.4                                (3) BF.sub.3 (3)                                      NF.sub.4 BF.sub.4 (6), prefluor. TiF.sub.4 (12)                                               170° C., 20h NF.sub.4 Ti.sub.2 F.sub.g (3.6),                           NF.sub.4 Ti.sub.3 F.sub.13 (1.6),                                                        BF.sub.3 (5.4), NF.sub.4 BF.sub.4 (0.6)               NF.sub.4 BF.sub.4 (6), prefluor. TiF.sub.4 (12)                                               170° C., 192h                                                                     NF.sub.4 Ti.sub.2 F.sub.9 (6),                        __________________________________________________________________________                              BF.sub.3 (6)                                     

Obviously, numerous variations and modifications may be made without departing from the present invention. Accordingly, it should be clearly understood that the forms of the present invention described above are illustrative only and are not intended to limit the scope of the present invention. 

We claim:
 1. A compound for use in an improved NF₃ --₂ gas generator, said compound having the general composition (NF₄ ⁺)nA^(n-), wherein A^(n-) is derived from SnF₄ and is self-clinkering.
 2. A compound for use in an improved NF₃ --F₂ gas generator, said compound having the general composition (NF₄ ⁺)nA^(n-), wherein A^(n-) is SnF₆ ⁻⁻ and is self-clinkering.
 3. A compound for use in an improved NF₃ --F₂ gas generator, said compound having the general composition (NF₄ ⁺)nA^(n-), wherein A^(n-) is SnF₅ ⁻ and is self-clinkering.
 4. A process for the poduction of (NF₄ ⁺)₂ SnF₆ ⁻⁻, comprising the steps of combining a soluble NF₄ ⁺ X⁻ salt with a soluble alkali metal salt of SnF₆ ⁻⁻ in a suitable solvent to produce an insoluble alkali metal X salt, and filtering off the precipitated insoluble alkali metal X salt from the solution containing the soluble (NF₄ ⁺)₂ SnF₆ ⁻⁻ salt.
 5. A process for the production of NF₄ SnF₅, comprising the steps of treating NF₄ BF₄ in an anhydrous HF solution with an equimolar amount of SnF₄ and removing all products volatile at room temperature. 